There are a couple of ways that scientists can date planets, so which planets formed first in our solar system?

Astronomers have been actively hunting for a ninth planet in the solar system for almost a decade. But a new study has ...

There has been a lot of back and forth about the existence of a mysterious ninth planet, often referred to as "Planet Nine" or even "Planet X." Now, though, researchers say there is likely at least a ...

A new study suggests yet another theory for a possible extra planet in our solar system, likely of a size between Mercury and ...

A newly discovered warp in the outer Solar System may have been created by a small, rocky world, much closer to the Sun than ...